Over the years, secondary batteries have been improved in many ways to provide increased life, greater vibration resistance, virtually maintenance free operation and other notable advantages. Nonetheless, one particular characteristic of such batteries has so far defied great improvement: sheer weight. Typically, prior art battery plates have comprised a grid of lead alloy which supports a positive or a negative active material or paste. The active materials interact with the battery electrolyte to produce electrical current which is carried from the plate to some sort of terminal via the lead alloy grid. From an electro-chemical point of view, it would be desirable to make the grid from pure lead metal; however, pure lead has very poor mechanical properties so that it usually has been alloyed with antimony or calcium, for example, to provide adequate strength. As is known in the art, these alloying materials interfere with the electrochemical reactions in the battery and can effect battery life considerably.
Attempts have been made in the past to reduce the amount of lead in a battery as a weight-saving measure. For example, Gulcher's U.S. Pat. No. 562,396 suggests the use of a woven grid of vertical lead metal wires and horizontal glass or quartz threads. However, since the plate is supported by the lead wires at its upper end, rather thick, heavy wires of pure lead or thinner wires of special alloys would have to be used to provide adequate strength to support the plate. In either event, the plate would be rather heavy. A more recent, somewhat similar approach is taught by Ikari et al in U.S. Pat. No. 3,944,431; however, the plate is still supported by its lead metal components, thus requiring the use of a considerable amount of lead for adequate strength. So, while the prior art does suggest ways of reducing the amount of lead in a battery plate, reliance on the use of the lead components for plate support has continued to necessitate the use of large amounts of lead.
Another recent approach to the problem of reducing the amount of lead is disclosed by Parkinson and Konishi in U.S. Ser. No. 731,137, filed Oct. 12, 1976 and assigned to Gould Inc., the assignee of the present application. The disclosure of Ser. No. 731,137 is hereby incorporated by reference in this application. As taught in Ser. No. 731,137, lead threads are woven or inserted into a web of material such as fiberglass. The web is then pasted with the required active material. The individual, separate plates produced in this manner are supported by appropriate attachments to a length of the material web which extends beyond the pasted area, rather than to the lead threads, so that very little mechanical stress is borne by the lead threads. The amount of lead in such plates may be reduced vastly, by as much as fifty percent (50%) in some examples; moreover, virtually pure lead can be used for the lead threads since alloying for strength is no longer necessary. Moreover, conductive materials such as tantalum, carbon fiber threads and others familiar to those in the art may be used in place of lead threads where suitable active materials are chosen. The plates disclosed in this application have many advantages; however, supporting the plates in a battery has presented some problems. The present invention concerns improved plates of the type disclosed in Ser. No. 731,137, which embody unique provisions for facilitating their installation and support in a battery housing, and also methods of making such plates.